The present application claims priority based on Japanese Patent Application No. 2003-158912, filed Jun. 4, 2003, the entirety of which is being incorporated herein by reference.
The present invention relates to a pneumatic tire taking into consideration recycling and retreading and to a method of scrapping the same. Specifically, the present invention relates to a pneumatic tire which facilitates separation of a rubber layer and to a method of scrapping the same.
In recent years, recycling of waste products is considered important. In order to increase the recycling rate without deteriorating physical properties of reclaimed materials, different materials require to be separated so as not to be mixed with each other. Moreover, separating materials requires being easy in order to save recycling costs and processing time.
A general pneumatic tire is composed of a rubber material and a cord of steel, organic fibers, or the like. Such a pneumatic tire has problems in recycling as follows.
Generally, tires are cut into pieces, and then materials thereof are separated from each other. The steel cord can be physically separated. However, the organic fiber cord is shredded and mixed into rubber, and different types of rubber are mixed with each other. Therefore, an installation is required which performs an aftertreatment for shredded rubber and separates the shredded rubber, and a lot of time is required for the aftertreatment. Moreover, mixture of a material with lower physical properties degrades the physical properties of reclaimed material.
On the other hand, another method is conceived in which a material softening at high temperature is placed between members and heated at high temperature in recycling to separate the members. However, in this case, the reclaimed material could be degraded by heating.
Meanwhile, a method (for example, see Japanese Patent Laid-Open Publication No. 5-154939) has been proposed, in which a cord is spirally wound and buried in a tread portion at 0 degree with respect to the tire circumferential direction and the cord is pulled out in the transverse direction.
However, in such a structure that the rubber layer is separated using the cord at 0 degree with respect to the tire circumferential direction, the circumferential elongation of the tire depends on the elongation of the cord, and the allowable amount of elongation thereof is limited. Therefore, the aforementioned separate structure is limited to only application to a portion which is elongated by a small amount in a tire building process. Moreover, to spirally wind the cord in the tire circumferential direction, it is required to continuously wind the cord, in a tire building process, leading to low productivity.